Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination
Abstract Background Microglia are the primary phagocytes of the central nervous system and are responsible for removing damaged myelin following demyelination. Previous investigations exploring the consequences of myelin phagocytosis on microglial activation overlooked the biochemical modifications...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
BMC
2021-12-01
|
| Series: | Journal of Neuroinflammation |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s12974-021-02360-3 |
| _version_ | 1819173868598722560 |
|---|---|
| author | Miranda M. Standiford Ethan M. Grund Charles L. Howe |
| author_facet | Miranda M. Standiford Ethan M. Grund Charles L. Howe |
| author_sort | Miranda M. Standiford |
| collection | DOAJ |
| description | Abstract Background Microglia are the primary phagocytes of the central nervous system and are responsible for removing damaged myelin following demyelination. Previous investigations exploring the consequences of myelin phagocytosis on microglial activation overlooked the biochemical modifications present on myelin debris. Such modifications, including citrullination, are increased within the inflammatory environment of multiple sclerosis lesions. Methods Mouse cortical myelin isolated by ultracentrifugation was citrullinated ex vivo by incubation with the calcium-dependent peptidyl arginine deiminase PAD2. Demyelination was induced by 6 weeks of cuprizone (0.3%) treatment and spontaneous repair was initiated by reversion to normal chow. Citrullinated or unmodified myelin was injected into the primary motor cortex above the cingulum bundle at the time of reversion to normal chow and the consequent impact on remyelination was assessed by measuring the surface area of myelin basic protein-positive fibers in the cortex 3 weeks later. Microglial responses to myelin were characterized by measuring cytokine release, assessing flow cytometric markers of microglial activation, and RNAseq profiling of transcriptional changes. Results Citrullinated myelin induced a unique microglial response marked by increased tumor necrosis factor α (TNFα) production both in vitro and in vivo. This response was not induced by unmodified myelin. Injection of citrullinated myelin but not unmodified myelin into the cortex of cuprizone-demyelinated mice significantly inhibited spontaneous remyelination. Antibody-mediated neutralization of TNFα blocked this effect and restored remyelination to normal levels. Conclusions These findings highlight the role of post-translation modifications such as citrullination in the determination of microglial activation in response to myelin during demyelination. The inhibition of endogenous repair induced by citrullinated myelin and the reversal of this effect by neutralization of TNFα may have implications for therapeutic approaches to patients with inflammatory demyelinating disorders. |
| first_indexed | 2024-12-22T20:29:55Z |
| format | Article |
| id | doaj.art-51cf6a9e5ba6479ca532c06010660dc7 |
| institution | Directory Open Access Journal |
| issn | 1742-2094 |
| language | English |
| last_indexed | 2024-12-22T20:29:55Z |
| publishDate | 2021-12-01 |
| publisher | BMC |
| record_format | Article |
| series | Journal of Neuroinflammation |
| spelling | doaj.art-51cf6a9e5ba6479ca532c06010660dc72022-12-21T18:13:37ZengBMCJournal of Neuroinflammation1742-20942021-12-0118111710.1186/s12974-021-02360-3Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelinationMiranda M. Standiford0Ethan M. Grund1Charles L. Howe2Neuroscience PhD Program, Mayo Clinic Graduate School of Biomedical SciencesNeuroscience PhD Program, Mayo Clinic Graduate School of Biomedical SciencesTranslational Neuroimmunology Lab, Mayo ClinicAbstract Background Microglia are the primary phagocytes of the central nervous system and are responsible for removing damaged myelin following demyelination. Previous investigations exploring the consequences of myelin phagocytosis on microglial activation overlooked the biochemical modifications present on myelin debris. Such modifications, including citrullination, are increased within the inflammatory environment of multiple sclerosis lesions. Methods Mouse cortical myelin isolated by ultracentrifugation was citrullinated ex vivo by incubation with the calcium-dependent peptidyl arginine deiminase PAD2. Demyelination was induced by 6 weeks of cuprizone (0.3%) treatment and spontaneous repair was initiated by reversion to normal chow. Citrullinated or unmodified myelin was injected into the primary motor cortex above the cingulum bundle at the time of reversion to normal chow and the consequent impact on remyelination was assessed by measuring the surface area of myelin basic protein-positive fibers in the cortex 3 weeks later. Microglial responses to myelin were characterized by measuring cytokine release, assessing flow cytometric markers of microglial activation, and RNAseq profiling of transcriptional changes. Results Citrullinated myelin induced a unique microglial response marked by increased tumor necrosis factor α (TNFα) production both in vitro and in vivo. This response was not induced by unmodified myelin. Injection of citrullinated myelin but not unmodified myelin into the cortex of cuprizone-demyelinated mice significantly inhibited spontaneous remyelination. Antibody-mediated neutralization of TNFα blocked this effect and restored remyelination to normal levels. Conclusions These findings highlight the role of post-translation modifications such as citrullination in the determination of microglial activation in response to myelin during demyelination. The inhibition of endogenous repair induced by citrullinated myelin and the reversal of this effect by neutralization of TNFα may have implications for therapeutic approaches to patients with inflammatory demyelinating disorders.https://doi.org/10.1186/s12974-021-02360-3MicrogliaMyelinCitrullinationTNFαRemyelination |
| spellingShingle | Miranda M. Standiford Ethan M. Grund Charles L. Howe Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination Journal of Neuroinflammation Microglia Myelin Citrullination TNFα Remyelination |
| title | Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination |
| title_full | Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination |
| title_fullStr | Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination |
| title_full_unstemmed | Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination |
| title_short | Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination |
| title_sort | citrullinated myelin induces microglial tnfα and inhibits endogenous repair in the cuprizone model of demyelination |
| topic | Microglia Myelin Citrullination TNFα Remyelination |
| url | https://doi.org/10.1186/s12974-021-02360-3 |
| work_keys_str_mv | AT mirandamstandiford citrullinatedmyelininducesmicroglialtnfaandinhibitsendogenousrepairinthecuprizonemodelofdemyelination AT ethanmgrund citrullinatedmyelininducesmicroglialtnfaandinhibitsendogenousrepairinthecuprizonemodelofdemyelination AT charleslhowe citrullinatedmyelininducesmicroglialtnfaandinhibitsendogenousrepairinthecuprizonemodelofdemyelination |